1. Field of the Invention
The invention relates to tooling for the preparation of round-conductor flat ribbon cables for subsequent termination (insertion) into electrical connectors. More particularly, the invention relates to an improved splitter for shearing the insulation web between the insulating jackets of adjacent conductors or groups of conductors in a flat ribbon cable.
2. Description of the Prior Art
In the prior art, and especially in the recent prior art, there have been various approaches taken to the problem of reducing the labor involved and therefore the cost of wiring and cabling of complex electrical and electronic equipment. That equipment nearly always comprises a number of subassemblies or plug-in modules which are interconnected with the other electrical subassemblies of a system. Such devices as computer systems involved large numbers of conductors running among the subassemblies or modules of the system, and removable electrical connections affecting large numbers of conductors must be provided.
The recent developments aforementioned include various forms of solderless connectors whereby a multi-conductor cable may be terminated in a connector much more quickly and with far fewer manufacturing operations than had previously been the case. A connector of the general type is referred to and described in U.S. Pat. No. 3,955,873. In that connector, the terminating posts or terminals are uniquely shaped as individual bifurcated elements into which insulated conductors can be discretely inserted. The slot formed by the bifurcated configuration is tapered and appropriately shaped along its inside edges so that in the process of inserting an insulated conductor therein for termination, the insulation is pierced (cut through) and a reliable electrical contact made. In lieu of individual wire connections, tooling, which may be a part of the assembled connector itself, can effect simultaneous termination of all of the conductors of a given cable, each conductor being terminated into a discrete predetermined bifurcated terminal post. The other extremes of each of the bifurcated terminals extend oppositely and provide the individual pins along the mating interface of the connector.
In U.S. patent application Ser. No. 664,487, entitled Electrical Connector, filed Mar. 8, 1976, an improved form of the connector of prior U.S. Pat. No. 3,955,873 is described. Among the improvements therein is the introduction of staggering of the aforementioned bifurcated terminals. That is, in a two-row pin arrangement, a pin-to-pin spacing in each row being aligned with the space between pins in the other row. Such a configuration is better adapted to the termination of flat ribbon-type cables, in that the insertion or termination of the conductors of the ribbon cable is facilitated. This is because alternate conductors pass between the terminals of the first row encountered to be terminated in a second row of terminals.
The solderless cable termination concept hereinabove described may otherwise be referred to as the "insulation displacement" technique and is particularly adapted to round-conductor, flat, ribbon cable. In such cables, the conductors are individually insulated, i.e., each has its own insulating jacket, and all of the connectors of the ribbon are joined in flat juxtaposition by webs, usually integral with the conductor insulation.
A frequently encountered problem arises from the fact that the center distances between contracts of the connectors hereinabove described is different from the center-to-center distances of the conductors of commercially available ribbon cables. For example, common commercially available connectors of the type described employ contact center-to-center spacing of 0.054 inches whereas the commonly available ribbon cable is fabricated with its conductor center-to-center spacing on the order of 0.050 inches.
It has been recognized that to terminate the conductors of the ribbon cable having 0.050 centers in the 0.054 centers connector contacts, the round conductors of such a flat ribbon cable must be split apart and dressed to the area directly above the individual contacts on the wider centers of the connector. That is, the web of insulating material joining the adjacent conductors or groups of conductors must be split for a predetermined distance along the length dimension of a ribbon cable to effectively "fan out" the conductors to the wider centers of the connector. Devices are known which comprise a series of facing cutters each having alternate blades basically of flat shape along the cutting edges running in the longitudinal cable dimension. These cutters are advanced against each other with a ribbon cable place between them. Such devices tend to alternately raise and lower the individual conductors or groups of conductors differentially causing a shearing action between them, thereby splitting the ribbon cable. Such devices are mounted on high leverage press-type equipment to accommodate the relatively heavy loads involved in this splitting operation.
It has been found that, due to the flat configuration of the individual blades of such devices, excessive loads are involved or excessive force is required to perform the splitting, particularly if a cable width of more than approximately 3/4 inches measured transversely is to be simultaneously split on a common 25 conductor ribbon cable. The excessive force required also has been found to cause damage and skewing of the individual wires and tearing of the individual jackets. The edges of the individual blades of the cutters are sharpened, but tearing action outside but adjacent to the axial or length dimension of the splitting desired (length of blades) is inevitable.
The manner in which the present invention reduces the operating forces required and greatly improves the quality of web-splitting in ribbon cable to be prepared for termination will be understood as this description proceeds.